1. Field of the Invention
The invention pertains to a pneumatic spring with a rolling bellows arranged between an outer tube and a roll rube, and at least one control valve with positions for feeding, blocking, and discharging compressed air. The control valve is actuated by a control element which acts on either the outer tube or the roll tube, and which has a working length which is shorter than the stroke of the pneumatic spring. The control element is supported in a floating manner relative to the outer tube and the roll tube, and is loaded by a first spring against one of the outer tube and the roll.
2. Description of the Related Art
U.S. Pat. No. 6,332,624 discloses a pneumatic spring with an integrated control valve, this control valve being actuated by a control element, the working length of which is shorter than the length of the stroke of the pneumatic spring. For this purpose, the control element is supported so that it floats in the axial direction and is pretensioned by a spring element so that the control element follows the stroke of the outer tube until a stop limits the further control movement of the control element, at which point the outer tube breaks the working connection with the control element.
Depending on the speed at which the control element travels outward, an audible sound, which can create a disturbing impression, is produced when the stop for the control element makes contact with the roll tube or with a component connected to this assembly. A similar effect can occur when the pneumatic spring returns to the desired level position from a point further outward and the outer tube re-establishes its working connection with the control element.
This problem does not occur in the case of the basic design according to U.S. Pat. No. 5,649,692, because the control element is permanently connected to the roll tube, which means that there cannot be any relative motion between these two components which could cause noise.